Rotary fluid supply system



Feb. 6, 1962 L. J. -M. GAMET ROTARY FLUID SUPPLY SYSTEM 5 Sheets-Sheet 1 Filed Feb. 1, 1960 w wm. hm. mm. Mm.

M S ii. m.. QM. SW w m ww :y n m WN WM.

Feb. 6, 1962 L. J. -M. GAMET ROTARY FLUID SUPPLY SYSTEM 5 Sheets-Sheet 2 Filed Feb. l, 1960 z'A/VE/vTa/Y Lou/'s Gama- Feb. 6, 1962 L. J. M. GAMET 3,020,057

ROTARY FLUID SUPPLY SYSTEM Filed Feb. 1, 1960 5 Sheets-Sheet 3 //'9.5 75\ 74 25a 266 se, g

Li u J 76 il' ii H Il 'I u L ruf/vers Feb. 6, 1962 J. M. GAMET ROTARY FLUID SUPPLY SYSTEM 5 Sheets-Sheet 4 Filed Feb. l, 1960 IN1/ENTI@ L 0 U/'s Game7- 5 Sheets-Sheet 5 L. J. "M. GAMET ROTARY FLUIDA SUPPLY SYSTEM Mdm /7 fda i l I m2 www' Feb. 6, 1962 Filed Feb. 1, 1960./

United States Patent C) 3,620,057 ITARY FHD SUPPLY SYSTEM Louis LM. Garnet, Bougival, France, assigner to La Precision Industrielle, Seine-et-Oise, France, a company of France Filed Feb. 1, 1969, Ser. No. 5,735 Claims priority, application France Feb. 12, 1959 11 Claims. (Cl. 279-4) This invention relates to an improved means of distributing a hydraulic fluid to a revolving fluid motor. More especially though not exclusively, the invention relates to such a fluid distributing system for use in machine-tool headstocks of the type incorporating a hydraulic motor rotatable with the spindle of the headstock, and serving to actuate a work-carrying chuck, or other power-actuated mechanism, during rotation of the spindle.

In some types of machine-tools, e.g. lathes, there is provided a liuid motor, for example of the cylinder and piston type, incorporated in the headstock and rotatable with the spindle of the machine-tool. Such incorporated tluid motor may serve for Various purposes including the actuation of a work-clamping chuck between its work engaging and disengaging conditions, the selective clamping and feeding of continuous bar stock through the machine, the machining of work in a jig carried by the spindle, or the like. The motor has to be supplied with uid from a stationary source of pressure fluid outside the machine `and a rotary distributor assembly has to be provided for permitting the flow of lluid from the stationary source to the revolving motor and back.

Thus, in my U.S. Patent No. 2,835,227, there was disclosedy a hydraulic cylinder and piston motor mounted on one protruding end of the machine-tool spindle and including a two-part distributor having one part rotatable with said motor and spindle and another, stationary, part surrounding said rotatable part and defining therewith an annular clearance space of narrow radial width. This clearance is provided suicient to prevent any mechanical friction between the rotary and fixed parts of the distributor while being small enough to introduce only an acceptably low pressure drop in the pressure of iluid supplied to the motor. The leakage ilow accompanying such pressure drop in thereby maintained within controlled bounds so as to permit recovery of the fluid leaking out of the distributor, preferably after having caused the leakage ilow to lubricate the distributor bearings. While the rotary distributor system disclosed in the said prior patent yielded satisfactory results in that it minimizedwear on the distributor parts, certain disadvantages exist due to its design. It is the primary object of the present invention to eliminate those disadvantages.

It will be understood that in distributor systems of the type here contemplated it is essential to maintain extremely precise centering between the two parts of the distributor. either side of the revolving distributor which bearings are then desirably lubricated by the leakage flow of iluid from the distributor as mentioned above. In the construction of the prior patent the provision of such special bearings in addition to the spindle bearings consumed considerable axial space for the distributor device, and the iiuid motor had to be mounted beyond the headstock at the end of the spindle remote from the chuck, or other mechanism to be operated byI the motor. This undesirably increased the length of the spindle. Further with the motor thus mounted it was necessary to provide a lengthy drive transmission from the motor to the chuck (or other mechanism) in the form of an axially reciprocating tube extending through the spindle. The

This involves providing roller bearings to ice ' presence of such tube reduces the useful inner diameter of the spindle and the axial reciprocations of the tubes may interfere with certain operations, bar-feeding for instance.

Objects of the invention are to provide a uid distributor system of the specified type which will be of considerably more compact construction than was heretofore possible; to provide such a system wherein no additional bearings will be required for the distributor, beyond those supporting the spindle in the headstock, or other frame'in which the system ofthe invention may be used; to provide such a distributor system for a machine-tool headstock wherein the distributor and motor may be mounted in directly adjacent relation to the chuck or other mechanism to be actuated thereby, thus doing away with undesirable mechanical drive transmissions such as tubes extending through the spindle.

Another important object is to facilitate the construction of the distributor assembly for a given, extremely narrow width of the annular clearance space between its stationary and rotatable parts. An object is to apply such a distributor system to various machine-tool headstock coniigurations.

Further objects of the invention are to provide means in such a distributor for blocking the uid within ther motor under a prescribed operating pressure, thereby preventing unwanted de-activation of the mechanism, eg. release of the work by the chuck, in case of defective fluid supply from the pressure source. Yet other objects will appear.

Exemplary embodiments of the invention Will now be described for purposes of illustration but not of limitation with reference to the accompanying drawings, wherein:

FIG. 1 is an laxial section of a machine-tool headstock incorporating a pressure fluid distributor, huid motor andv FIG. 5 is a simplified outline view, to a reduced scale,

ot a lathe embodying a central or double-ended headstock arrangement;

FIG. 6 is a similar view of a machine-tool for machining both ends of elongated stock, e.g. lengths of tubing;

FIG. 7 is a similar view of a lathe embodying bar feedv mechanism; the last three figures being all illustrative of types of machine-tools to which the invention is supplied,.-

FIG. 8 is a partial end view of the outer ring member of a distributor system according to another embodiment of the invention;

FIG. 9 is a plan view of the embodiment of FIG. 8 as seen in the direction shown by the arrow IX in the latter figure;

FIG. l0 is a sectional view on the broken line X-X of FIG. 9 illustrating the last-mentioned embodiment; and FIG. 1l is a partial View on line Xl-XI of FIG. l0. Before proceedingwith the particular description with reference to the drawings, the main aspects of the invention will be explained in general terms.

ln order to provide a more compact rotary distributor structure wherein a common set of bearings is used both for supporting the spindle and the distributor, the invention contemplates providing a pair of spaced roller bearings having a common stationary outer race ring member formed with a cylindrical internal surface intermediate its length with at least one pressure fiuid delivery orifice opening radially into said surface, said bearings having separate, axially spaced inner race ring members. Between such inner race rings is mounted a spacer ring member having an outer cylindrical surface defining an extremely narrow radial clearance space with an inner cylindrical surface of the stationary common outer ring. The said rotatable inner race ring members and the intermediate spacer ring member are mounted in a close fit on a cylindrical section of the spindle, and means are provided for exerting an axial clamping pressure on the three juxtaposed members for bodily rotation thereof with the spindle. A pair of interconnected circumferential grooves are defined respectively by the outer and inner cylindrical surfaces of the intermediate spacer ring member, respectively with the inner cylindrical surface of the stationary outer ring member, and with the cylindrical surface of the spindle, which grooves are both formed in a common axial plane corresponding with that in which said fluid delivery inlet orifice delivers, and both grooves being interconnected by at least one generally radial duct formed through the rotatable inner ring member. The inner one of said grooves communicates with at least one generally axial passage formed through the spindle and leading t the fluid motor carried by the spindle.

It will be clear that since both bearings embody a common outer stationary ball race, an accurate coaxial and concentric relationship can easily be provided between the outer circumferential roller race surfaces and the cylindrical intermediate surface constituting the stationary part of the distributor, by simply boring the inner surface of said common stationary Outer ring. Similarly, an accurate coaxial and concentric relationship is readily had between the inner circumferential roller race surfaces and the cylindrical surface of the intermediate ring member constituting the rotatable part of the distributor, by simply grinding the surface of the cylindrical spindle section. This accurately centered relationship will in turn ensure that the intermediate spacer ring can revolve in very closely spaced relationship with the outer ring surface, a radial clearance distance on the order of one or two hundredths of one millimeter being readily achievable. The pressure liuid can thus be led from the inlet through the outer groove and through the inner groove and thence into the spindle passage leading to the motor at the cost of low controlled laminar leakage through the gap between the outer and inner ring members, the leakage flow as being collected and used for lubricating the roller bearings supporting the spindle.

Furthermore, owing to the steep axial pressure gradient, i.c. the high rate of pressure drop per unit axial length along the ow path through the gap between the coaxial ring surfaces, it becomes possible to provide parallei flowpaths side by side in axially spaced transverse planes, between the spaced roller bearings. Thus there can be provided two such parallel fiowpaths leading to the opposite ends of a double-acting cylinder-and-piston motor or jack, without having to impart an excessive axial length to the intermediate spacer ring. Conversely, in view of the short axial length of the spacer ring, it becomes possible to position the bearings close to each other, thereby to minimize the objectionable effects of longitudinal expansion of the spindle on the centering thereof in its roller bearings. In practice, the spacing selected between the bearings would be just sufficient to ensure a firm support of the spindle without the provision of auxiliary bearings. The spindle may be provided comparatively very short, whereby machining of its inner bore from either end of the spindle as far as4 its central distributorforming portion can very simply and conveniently be performed.

In carrying the invention into effect according to one embodiment, as shown in FIGS, l and 2 of the accompanying diagrammatic drawings, -a spindle 1 of a headstock 2 of a machine-tool, such as a lathe, is supported lin two axially spaced taper roller bearings, the bearing assemblage advantageously being constructed in accordance with the prior Patent No. 2,499,640 and comprising a common external ring 3 having two internal rolling surfaces 3a, 3b of truncated conical form, and a central cylindrical surface 3c. Internal rings 4, 5 of the two roller bearings and an intermediate or central spacer ring 6, are fixedly positioned on the spindle 1. The rollers 7, 8 of the bearings are respectively enclosed in cages 9, 10 which may be retained on the internal rings 4, 5 by steel wire rings 11 during mounting of the spindle I in the headstock 2. In assembling the headstock, the three internal rings 4, 5 and 6, with the cages 9, 10 of the rollers 7, 8 carried by the rings 4, 5 are inserted in the external ring 3 and the whole assembly is placed on the spindle 1. The assemblage is then inserted into the headstocl: 2, the angular position of the external ring 3 being defined by a spigot 42 the head of which engages in a rounded recess in an external tiange 3d of the ring 3.

As shown in FIG. 1, the external ring 3 is provided with two circumferential grooves 12 and 13 for receiving oil under pressure from channels 14, 15 respectively. Each of the grooves 12, 13 communicates with the inernal cylindrical surface 3c through a series of radial holes 16. These holes 16 are opposite grooves 17 and 18 respectively, which are provided in the central ring 6. Through the medium of the radial holes 19, the external grooves 17 and 18 of the central ring 6 are connected to internal grooves 20 and 21 of the latter.

From opposite the groove 20 two channels 23 (see FIG. 2) in the spindle 1 extend to the front face of a back plate la on the nose of the spindle 1. In the same manner, from opposite the groove 21 two opposite channels 24 extend in the spindle 1 and are offset so as to terminate at orifices 25 in the front face of the back plate 1a.

On the back plate 1a a chuck 26 is xed by means of three pairs of screws 2'! (see FIG. 2) which traverse the chuck from front to back. Peripheral packing 28 ensures oil-tightness of the joint.

The face of the chuck turned towards the spindle is provided with a cavity 29 which, with the front face of the back plate 1a, forms an annular ram cylinder in which an annular piston 3f) of a hydraulic jack is slidable. Packings 31 and 32 hermetically seal an extending central part of this piston in the interior of the spindle 1 and an oppositely extending part in the interior of the chuck 26. A packing 33 forms a seal at the periphery of the piston 30 in the cavity 29.

ln the body of the chuck 26 and diametrically opposed to one another, are arranged the two series of holes 34, each forming a U-shaped channel, of which one of the terminal orifices 34a registers with one of the orifices 25 in the front face of the back plate 1a. A centering pin 35 (FIG. 2) projecting from the back plate 1a registers with a blind cavity in the rear face of the chuck to prevent incorrect positioning ofthe chuck on the spindle, which would not ensure registering of the orifices 25 and 34a.

The piston 30 is prevented from turning in its housing by a pin 36 which engages in a recess in the rear face of the cavity 29.

The front part of the piston 30 comprises three cavities 37 spaced at 120 from one another and in which there are housed cylindrically faced ends 38a of bellcrank levers 38 movable around pivots 39 and carried by the chuck 26. The other ends 38h of these levers 38 also are cylindrically faced and are engaged in the housings 49a of jaw-holders 40 which, by means of screws 41, support the chuck jaws.

At the inner side of the chuck 26 leakage of oil towards the exterior is prevented by an annular connecting part 43 between the periphery of the back plate 1a and the headstock 2. This part 43 is fixed to the headstock 2, with the interposition of joint packing 44, by screws (not shown) suitably spaced. It is provided with an oil-retaining groove 45 around the spindle 1 opposite a peripheral `slot therein. An oriiice 45a, arranged at the lowest point of this groove 45, permits return of oil received by the groove 45 to a collecting reservoir through a cavity in the annular part 43 and a channel 47 connecting therewith. A similar groove 46 surrounds the back plate la to prevent infiltration of the cutting or coolant liquid towards the interior of the headstock, any infiltration being passed to the exterior through a channel 46a.

In the embodiment shown, the spindle l carries, on the left-hand in FIG. l, a gearwheel Sii which is prevented from turning by a key 51. A threaded ring 52 with grub screw 52a presses against a shoulder 1b of the spindle 1, the assembly of the rings 4, 5 and 6 and the gearwheel 5l), so as to prevent any longitudinal displacement of the assembled units and rotation of the rings 4, 5 and 6 on the spindle 1.

The gearwheel Sil (and the gearw-heels which drive it) may be enclosed in an oil-tight gearcase.

The function of the assembly above described is as follows:

Owing to the precision of centering of the spindle 1, by the taper rolle;- bearings, the internal `diameter of the cylindrical surface 3c, and the external diameter of the ring 6 can -be selected so that the annular space which separates them is very small, for example, of the order of one to two hundreths of a millimeter.

Thus, when oil is fed under pressure through one of the channels 14 or 15, yand passes into the appropriate groove 12 or 13 and thence through the channels 16, the groove 17 or 18 is likewise placed under pressure and a small quantity of oil escapes from each side of this groove into the annular clearance space which separates the ring 6 from the surface 3c. This oil expands in this space and arrives at practically atmospheric pressure, either at the inner end of the right-hand roller bearing, or in the adjacent groove 17 or 18 whe-re it is collected.

From the groove 18 oil under pressure passes through the radial holes 19 into the internal groove 21 and, from the latter, into the two diametrically opposite channels 24. From there the oil under pressure enters one of the compartments of the cavity 29 of the jack, in the example the right-hand compartment 53, which displaces the piston 30 towards the left and, in consequences, drives the jaw-carriers inwards for tightening the chuckl jaws on a workpiece.

lf oil under pressure is fed through the channel 15, the piston 30 is displaced towards the right.

It will be noticed that elimination of any mechanical connection between the operating jack and the tightening members renders it possible to leave the internal channel of the spindle 1 completely free for the passage of stock or parts to be machined.

By the peripheral grooves 12 and 13 the oil is distributed to all the radial channels 16 and an effect of concentric pressure on the periphery of the ring 3 is secured which prevents any distortion of the latter capable of causing seizing on contact with the ring'6 owing to the very small distance which separates the internal face of the ring 3 from the said ring 6. ln the same way, the similar internal and external grooves of the ring 6 play a similar role in the uniform distribution of the ow of liquid and maintaining equilibrium of forces and, moreover, they render it possible to obtain without special precautions at the time of mounting, registering of the orifices in the wall of the spindle (ends of the channels 23 and 24) with the oil feed passages.

In the embodiment described, the right-hand bearing (rollers 8) is lubricated by leakage of oil only when the groove 12 is under pressure, and the left-hand bearing (rollers 7) only when the groove 13 is under pressure because, in both cases, the leakage of oil which escapes from one groove 17 or 18 towards the other is collected by the latter and evacuated. There is therefore a risk 6 of inadequate lubrication of the roller bearings which support the entire load of the machine.

To overcome this drawback, the external ring 3 may be provided with oil feed orifices 54 and 55 which emerge adjacent the small diameter end of each of the conical bearings. `Oil fed through these channels traverses the said conical bearings, and especially the internal holes of the rollers 7 and 8, to be expelled, after its lubricatingk and cooling elect. to the outside of the roller bearings'.

The orilices 54 and 55 can be fed with oil om any source but preferably are fed withthe same oil which is utilised in the hydraulic circuits, since the two oils are mixed in the collecting sump.

From the sump 56, which contains the reserve of oil, a pump 57 feeds oil under pressure through the channels 14 and 15 along the path shown by the dotted lines 58, and including a distributor which is not shown. However, for proper working of the jack, the pressure of oil supplied by the pump must be regulated to a predetermined value. `For this purpose there is used in known manner a pressure-regulating or relief valve 59 comprising a flap 6l) closed by a spring 61, the thrust of which is adjustable. When the pressure of oil delivered by the pump 57 exceeds the thrust of the spring 61, the oil passes into the upper compartment of the valve 59. It is then led through a pipe 62 to the orifices 54 and 55.

As the rate of discharge of the valve 59 is practically constant (except at the moment when the piston 30 is displaced), the roller bearings are permanently lubricated.

Moreover, as long as a part to be machined is grippedy by the jaws of the chuck, this grip is maintained by the pressure of the liquid in the jack, so that, in contradistinction to chucks incorporating irreversible tightening,"y

there is no risk of inadvertent release of the part through loosening of the jaws.

It is, however, possible to ensure correct lubrication of the bearings which carry the spindle 1 without making use of a supplementary oil feed. As shown, for examplej in FIG. 4, a bleed passage 65 communicates with the groove 17 and extends to the inner end of the right-hand roller bearing. Similarly, a bleed passage 66 communicates with the groove 18' and extends to the inner end of the left-hand roller bearing. 'Ihe grooves 17, 18' are placed under pressure alternately and when, for example, the left-hand groove 17 is under pressure, leakage which takes place towards the left-hand bearing, in the space between the rings 3 and 6, is suicient to lubricate this bearing, and a certain quantity of oil passing through ,the bleed passage 65 lubricates the right-hand bearing. Conversely, when the right-hand groove 18 is under pressure, the right-hand bearing is lubricated by leakage andE the left-hand bearing by oil which flows through the bleed passage 66. f

The leakage paths and the bleed passages 65, 66 can be calibrated in such a way that, for normal working of the machine, lubrication of the twov bearings is tially equal and adequate.

The arrangement of bearing assembly to provide a rotary distributor for oil under pressure is particularly4 appropriate in a lathe having a central or double-ended headstock, that is, a headstock provided with a chuck at each end of the spindle for engaging parts which traverse the spindle.

The two jacks of the chucks can be connected by suitable holes in the spindle extending in opposite directions, as is shown in FIG. 3. In the embodiment, the ring 3 yhas three Series of holes I671, 672 and 673, which feed grooves 681, 682 and 633 of the ring 6. The grooves 681 and 663 correspond to grooves 691 and 693 provided in the spindle 1, which communicate with the holes 70 and i1 for feeding oil under pressure for operation of jacks at the ends of the spindle 1 in the direction of the tightenf ing of the corresponding chuck. The central groove 6924 of the spindle, which communicates with the groove 6824 of the ring 6, also communicates with a channel 72 common to the two jacks which permits loosening.

In this case, while the jacks are being put under pressure for tightening, that is, during the working phase of the machine, leakages towards the left from the groove 681 and towards the right from the groove 633, are sufiicient for lubrication of the roller bearings 7 and 8. During the phase of loosening, when the load on the machine is less, the lubrication is momentarily interrupted because the grooves 681 and 683 are released from pressure and only the groove 652 is under pressure.

FIGS. 5 to 7 illustrate other possible modifications.

In FIG. 5, a central headstock 74 incorporates a driving motor which, through a transmission 75 by belt, chain or gearwheel, drives the internal spindle 1 which is provided, at its two ends, with chucks 26a and 26h. A part 76, which traverses the headstoclr, can thus be machined at both ends by tools mounted in tool-holders 77a and 77b.

In the modification shown in FIG. 6, each of two head- .i

stocks 78 and 79 carries a spindle provided at its ends with a chuck 26a and 26h respectively. The two spindles are connected by a tube 80 which ensures their being driven simultaneously. In this tube 80, a length S1 of bar or tube may be accommodated while being machined at both ends which are held in the chucks 26a and 251).

As shown in FIG. 7, a tubular spindle S2 is carried by two bearing assemblies S3 and 04, such as described with regard to FIGS. l, 3 and 4. The rotary distributor of the bearing assembly 84 feeds oil under pressure for operating the chuck S5, while the rotary distributor of the bearing assembly 83 feeds oil under pressure for operating a bar-feed device 86 of known type comprising automatic tightening clamps for a bar or tube 37 and hydraulic jacks for me longitudinal displacement of these clamps. During the operation of the tool mounted in the hooi-holder 88, the bar or tube is held by the chuck 85. When the part after machining is cut from the tube of bar 87, the chuck is loosened and the bar-feed device comes into action to move the bar forward by the length of a new part to be machined. The combination of the operation of a hydraulic motor of a chuck and of a barfeed device can be obtained by means of end-of-stroke limit switches actuating electro-vales or by manual con tacts or by a combination of these two methods.

In those applications of the invention where the fluid motor incorporated with the rotatable spindle is used to operate a work clamping chuclf. or the like, it is usually important that the supply pressure to the motor be permanent. sure fiuid supply circuit, it would be very undesirable for the chuck to be suddenly disengaged and release the work during rotation of the machine-tool.

According to an important feature of the invention, this possibility is averted by providing means for blocking the pressure fluid in the motor in an engaged condition of the mechanism operated thereby.

For this purpose, the invention contemplates providing valve means for selectively controlling the communication between an outer and an inner annular groove of the intermediate ring member. The valve may assume the form of an axially displaceable plunger spring-biassed in a direction to seal such communication, and exposed to the pressure of the fluid in the outer groove to move in the opposite direction for opening said communication. A further plunger member may be provided for similarly controlling a communication between the grooves for blocking the return fiow of fluid from the motor to exhaust.

FIGS. 8 to l1, illustrating a lform of the invention in which the last described features are embodied will new be described.

The construction shown in the figures is generally similar to that previously described lwith reference to FIGS. 1 and 2, and corresponding components have been In case of an accidental 4failure in the presc: designated by similar reference numerals. It will be seen from FIG. i0 that the stationary common outer ring member 3 is provided with two threaded fiuid connections 14 and 15 to the fluid supply line. Cooperating with an arcuate recess formed in the peripheral end fiangc 3d of said ring member is a spigot 42 serving to locate the angular position of the ring 3 in the headstock frame. Just as in the embodiment shown in FIG. l, lubricating orifices 54 and 55 are formed through the ring member 3 which discharge into proximity with the taper rollers of the bearings.

The connections 14 and 15 respectively open into the two axially spaced grooves 17 and 18 formed in the inner periphery of ring member 3. The spacer' member 6 interposed between the inner race ring members 4 and 5 of the bearings and rotatable with the spindle is formed with internal annular grooves 20 and I1 which respectively register in axial position with the grooves 17 and 18. The inner grooves 20 and 21 respectively communicate with the axial passages 23 and 24 formed in the spindle and leading to the opposite ends of an hydraulic motor carried by the spindle, such as a cylinder and piston motor similar to that shown in FIG. l.

The groove 17 is connected with groove 20 through a first radial duct 90, which is intcrsected by an axial bore 96 formed through the member 6, and is further connected with said groove 20 through a zigzag passageway comprising the oblique passages 91a and 9Ib and the intersecting axial bore 92 (see FIG. 11) yformed in the ring member 6. In a similar way the groove 18 is connected with the groove 21 through a first radial duct 93 intersected by axial bore 97 (see FIG. 1l), and by a second zigzag passageway comprising the oblique passages 94a and 94b intersected by axial bore 95 formed in ring member 6 (FIG, l0).

Slidably positioned in the axial bores 92 and 95 forming part of the zigzag passageways are valve plungers 9S and 99 respectively. The plungers 98 and 99 are biassed in opposite directions by compression springs 100. These .bias springs are seated at one end against perforated plugging members 101, and at their opposite ends against imperforate plugging members 102.

The plungers 98 and 99 are formed with stop pins 98a and 99a respectively, preventing the plunger end faces directed towards the imperforate plugs from engaging the latter.

Similarly, slidably positioned in the bores 96 and 97 are the valve plungers 103 and 104 mounted between an imperforate and perforate plugging members 102 and 101 and urged by bias springs 100 towards the imperforate plugs 102. Each of these plungers 103 and 104 includes a reduced diameter intermediate section, 103a and 104a respectively, and an end stop member, 103i: and 104i respectively, serving to provide pressure chambers betwen the imperforate plugging members and the corresponding end faces of the plungers. The pressure chambers are pressurized through the bores 105 and 106 with fluid from the respective outer grooves 1.7 and 18.

It will be noted that the plungers 98 and 104 associated with groove 17 are both oriented in one common direction while the plungers 99 and 103 associated with groove 13 are both oriented in a common direction reverse from the first.

In operation, when pressure fluid is delivered by way of inlet connection 14, the fluid flows from groove 18 through bores 94a and 106 and acts on both plungers 99 and 103 to urge them leftward (as in FIG. l0), so that a communication is established from said inlet groove through zigzag passageway 94a, 95, 94h to the passage 94, and another communication is established from the passage 93 for the exhaust fiow of fluid, to groove 18, by way of the passage defined by the reduced-diameter section 103e and radial duct 90. Thus, the hydraulic motor will be operative even in the event that the exhaust pres- 9 sure in groove 17 should be insudcient to urge the plungers 98 and 104 to the right (as in FIG. ll).

Conversely, when pressure is supplied through the connection 1S, then the plungers 98 and 164 are urged rightward and the operation of the motor is permitted even if plungers 99 and E03 are not urged leftward due to inadequate pressure from the groove 18.

Thus, the bias springs lili) may be calibrated so as to determine some suitable intermediate pressure in the range between the inlet pressure and the exhaust pressure. In such an arrangement, should there occur an accidental drop in pressure in that part of the external fluid circuit supplying the particular connection 14 or 15 that was pressurized, the pair of plungers associated with that connection are both moved to sealing position; since the other pair of plungers (asociated with the other fluid connection) were both moved to sealing positions due to the effect of the return or exhaust pressure, it is seen that all the connections between the motor and the external supply circuit are eiectively blocked, and the motor is thus positively locked in its present condition. Thus the arrangement just described provides for a fully positive and irreversible operation of the motor.

However, in a desirable modification of this aspect of the invention, it is contemplated that the bias springs may be calibrated so as to move the plungers to their sealing positions only for a pressure lower than the return or exhaust pressure. In such case, the motor is rendered irreversible (or self-locking) only as concerns such faults in the supply system as may involve the part of the system between the pump and the distributor. In such case the plungers will at all times assume their open positions during normal operation and will only be moved to sealing condition in the event of a pressure drop simultaneously occuring in both sides of the pressure system connected to the respective lines 14 and l5.

Such a modification offers a number of advantages. For in the iirst place, it is for all practical purposes substantially as safe as the arrangement rst described, since faults are much more liable to occur in the hydraulic lines between the pump and distributor (including the latter) than in the portion of the circuit beyond the distributor and to the exhaust sump. On the other hand, with such an arrangement the plungers will normally remain stationary throughout operation of the system and will only e actuated in the relatively unfrequent event of a defect. Wear is thus reduced and service life is greatly extended. Moreover, since a permanent communication is now present between the opposite sides of the motor and the distributor and the pressure source (just as in the absence of any locking valve arrangement), a possibility is made available which was not provided in the closed-center type of operation previously described. This possibility, now to be described, is of especial advantage in connection with lathes and similar machine-tools on which work may have to be exposed to more than one roughing and iinishing passes.

In such cases, during the roughing pass or passes the work required to be clamped under extremely high pressure in the chuck to prevent any displacement of it by the tool, and such high clamping pressure may tend to cause some amount of distortion in the workpiece. It then becomes imperative, before commencing a finishing pass, to relieve the workpiece of any such distortion, and experience shows that for such purpose it is not suicient just to relieve the supply pressure to the chuck actuating motor, but it is necessary to exert a brief yet relatively thorough disengaging action to permit a complete relaxation of the st'rains present in the workpiece before reengaging the chuck for the finishing pass. Such an eiiect can be obtained by imparting a sudden to-and-fro action to the distributor to reserve momentarily the huid pressure acting in the opposite sides of the motor. However, such an operation cannot be successfully performed if the oil pressure has to displace the valve plungers, since the inertia opposed by the plunge-rs to such displacement would introduce a substantial lag into the response time of the motor thereby preventing the desired rapid reciprocation of said motor and the chuck actuated thereby. There are, of course, various other circumstances in which one or the other of the two arrangements described above may be found more convenient, depending on the particular application.

It will be noted that in those forms of the invention described with reference to FIGS. 8 to 1l, the plungers are arranged for displacement in axial directions so that their displacements are not affected by centrifugal forces which might otherwise undesirably modify the biassing forces applied to the plungers.

in all cases, when the valve plungers have been moved to their sealing positions, the pressure fluid is entrapped in the compartments of the fluid motor due to the sealing of the spindle passages such as 23 and 24, so that the piston or other `displaceable element of the motor is positively locked in position.

While only two such passages 23 and 24 have been shown for connecting the distributor with the motor, it will be understood that more than two may be provided in parallel in order to increase, if desired, the totai flow section and thus permit higher rates of oil flow for increasing the rate of response of the motor.

Various other modifications will occur to those familiar with the art, in particular, various features of` the embodiments shown may be combined in other ways' than those speciiically disclosed, without exceeding the scope of the invention.

What I claim is: v

1. In ya machine-tool including a stationary frame, a rotatable spindle 4having a cylindrical portion and at least one axially directed bore, and a yiiuid motor bodily rotatable with said spindle and operatively connected with the opening of said bore, the combination of a pair of axially spaced roller cages, each including a set of regularly distributed taper lroliers, said cages having their smaller diameter ends facing one another; a stationary outer-ring fitted in said frame, secured against rotation therein and surrounding said cages and rollers, and having spaced outer-race ways for said sets of rollers and a cylindrical inner surface therebetween; `a set of' three coaxially juxtaposed annular members having cylindrical inner faces iitted about said cylindrical portion of said spindle, both outer members being each provided with an inner-race way respectively for said sets of rollers and the middle member having a cylindrical outer surface defining with said cylindrical inner surface an annular gap of narrow radial width; axial tightening means carried by saidspindle Ifor securing said set of members to said spindle for rotation therewith; an external pressure iiuid system; oritce means in said outer ring connectable with said huid system; iirst annular groove means defined between said cylindrical inner and outer surfaces and registering with said orce means; second annular groove means coplanar with the former between said cylindrical inner face of said middle annular member and the outer surf-ace of said cylindrical portion; radial duct means connecting respectively tirst and second annular groovemeans and said second groove means with said axially directed bore, whereby when under pressure uid of said system feeds said uid motor and a minor portion of said iluid passing through said annular gap cools and lubricates said roller bearings; and means supplied by said fluid system for further cooling `and lubricating said roller bearings.

2. The combination according to claim l wherein said taper rollers are axially bored for providing uid passages therethrough.

3. The combination according to claim l wherein said stationary outer-ring is provided with substantiaily radial bores at the inner limit of the outer-race way thereof, wherein said external Huid system comprises a sump for said fluid, a fluid pump, duct means connecting said pump to said orifice means land relief valve means for regulating the fluid pressure and wherein .the means for further cooling and lubricating said roller bearings comprise further duct means connecting the outlet of said relief valve means with said radial bores.

4. The combination claimed in claim l, wherein said fluid motor comprises a coaxial ram motor carried by the spindle, and further comprising a chuck assembly carried by the spindle yadjacent to said ram motor and connected thereto for operation thereby between an engaging and a disengaging condition.

5. In a machine-tool including a rotatable spindle having a fiuid ram bodily rotatable therewith, the combination of a pair of axially spaced roller bearings supporting the spindle; a common stationary outer ring surrounding the rollers of said bearings and defining outer-race surfaces therefor; an inner ring between the bearings and rotatable with the spindle, and having an annular cylindrical outer surface defining with an annular inner surface of said outer ring a narrow annular clearance gap; an external pressure fluid system; first orifice means in said outer ring connectable with said system to operate said ram to a selected condition; second orifice means in the spindle connected with said ram; groove means defined between said annular surfaces and registering with said first orifice means; radial duct means in the inner ring connecting said groove means with said second orifice means; and valve means interposed in said duct means and movable in response to pressure in said orifice means in a direction to permit fiow through said duct means and means biassing said valve means in a direction to block the fiow to thereby lock said motor in a selected condition thereof in the event of a drop in said pressure.

6. In a machine-tool including a rotatable spindle having a fluid ram bodily rotatable therewith, the combination of a pair of axially spaced roller bearings supporting the spindle; a common stationary outer ring surrounding the rollers of said bearings and defining outer race surfaces therefor; a recessed inner ring between the bearings and rotatable with the spindle and having `an annular outer surface defining with an annular inner surface of said outer ring a narrow annular clearance; an external pressure fluid system; a pair of first orifices in said outer ring selectively connectabie with a highand a low-pressure side of said system to operate said ram to a selected condition; a pair of second orifices in the spindle connected with opposite sides of said ram; a pair of grooves defined between said `annular surfaces `and registering with said first orifices; ducts in the inner ring connecting said groovm with the respective second orices; and valve means movably positioned in said recessed inner ring so as to be moved to a first position in response to pressure in one of said first orifices for permitting flow through la related duct to permit operation of said motor to -a selected condition, and means biassing said valve means to another position for preventing flow through said duct to lock said ram in its selected condition in case of a drop in said orifice pressure.

7. The combination claimed in claim 6, wherein said valve means comprise a first and a second pair of valve members, the members of each said pair being respectively responsive to high pressure present in a corresponding one of said first orifices to be moved to positions permitting fiow from the groove relating to said one `first orifice towards the related second orifice, and from the other second orifice towards the groove relating to said other first orifice.

8. The combination claimed in claim 7, wherein said valve members comprise plungers movable in bores formed in said inner ring in directions parallel to the spindle axis.

9. The combination claimed in claim 6 wherein the means hiassing said valve means are adjusted for preventing flow through said duct for a uid pressure in said first orifices lower than the low pressure of said pressure fluid system.

l0. A head-stock assembly for a machine-tool comprising a head-stock frame; -a stationary outer-ring fitted into said frame and secured against rotation therein, said outer-ring having two outwardly flaring outer-race ways for taper rollers and a cylindrical inner surface therebetween in the middle part of said outer-ring and further having a pair of axially spaced apart first recessed duct means in said middle part; `a pair of roller bearing cages, each including a set of taper rollers respectively cooperating with said outer-race ways; an axially bored rotatable spindle having a cylindrical outer portion and a pair of axially directed blind hores starting from one end of said spindle; a set of three coaxially juxtaposed annular members having cylindrical inner faces fitted about said cylindrical portion of said spindle, both outer iembers having each `an inner-race way respectively for said sets of rollers and the middle member having a cylindrical outer surface defining with said cylindrical inner surface of the said outer-ring an annular gap of narrow radial width having a pair of recessed grooves respectively registering with said pair of first recessed duct means, said middle part further having a pair of second radially directed duct means respectively issuing from said grooves; axial tightening means carried by said spindle for securing said set of members to said spindle for rotation therewith; a chuck assembly inciuding an annular double-acting ram motor secured to said end of the spindle; further duct means for respectively connecting each compartment of said double-acting ram to one of said blind bores; an external pressure fluid system having high and low-pressure sides; pipe means connecting respectively said sides to said first duct means; third duct means including peripheral groove means connecting respectively said second duct means to said blind bores; gearing means for rotating said spindle cooperating with the part thereof which is, with respect to the bearings, opposite to that which carries the chuck assembly and duct means supplied by said fiuid system and issuing towards the smaller diameter of said roller bearings for cooling and lubricating thereof.

lll. A head-stock assembly for a machine-tool comprising a head-stock frame; a stationary outer-ring fitted into said frame and secured against rotation therein, said outer-ring having two outwardly aring outer-race ways for taper rollers and a cylindrical inner surface therebetween in the middle part of said outer-ring; a pair of roller bearing cages, each including a set of taper rollers respectively cooperating with said outerrace ways; an axially bored rotatable spindle having a cylindrical outer portion and .two pairs of axially directed bores, each pair issuing at one end of said spindle; a set of three coaxially juxtaposed annular members having cylindrical inner faces 'fitted `about said cylindrical portion of said spindle, both outer members having each an inner-race way respectively for said sets of rollers and the middle member having `a cylindrical outer surface defining with said cylindrical inner surface of the said outer-ring an annular gap of narrow radial width; axial tightening means carried by said spindle for securing said set of members to said spindle for rotation therewith; a chuck assembly including an annular doubleacting ram motor secured to each end of the spindle; duct means for respectively connecting one axial bore of the spindle to one compartment of said motor rams; an external pressure fluid system having high and low pressure sides; a set of at least two spaced apart first duct means in the middle part of said outer-ring connectable with said sides of said system; first annular axially spaced apart groove means dened between said cylindrical inner and outer surfaces and registering with said first 13 Y 14 duct means; second radially directed duet means in ameter of said roller bearings for cooling and lubricating said middle member issuing from said first groove means; thereof. and third duct means including second groove means and respectively coplanar with the rst groove means References Cited In the 51e 0f fhlS Patent for connecting one of said rst groove means with one 5 UNITED STATES PATENTS of said axial bores of 'the spindle; gearing means located between one chuck assembly land the nearer roller bear- 2674461 Gamet Apr' 6 1954 in7 for rotatinur said spindle and duct means supplied 2835227 Garnet May 20 1958 a c 2,880,009 G-amet Mar. 31, 1959 by said iluid system and issuing towards `the smal-ler di- 

